1. Field of the Invention
The present invention relates to motherboards for computers, particularly to a motherboard configured to prevent or minimize damage to a semiconductor chip on the motherboard when the motherboard suffers an impact.
2. Description of Related Art
In the design process of a motherboard, stability of chips on the motherboard is a prime concern. In manufacturing of a motherboard, semiconductor chips are usually mounted on a printed circuit board via tin balls. A conventional tin ball is made with lead. Because of good capability of lead for resisting shock, the tin ball is not easily damaged. However, due to the dangers of leaded tin balls polluting the environment and damaging health of people, nonleaded tin balls are now commonly used in the process of mounting a semiconductor chip to a printed circuit board. However, because of the poor capability of non-leaded tin balls to resist shock, they are easily damaged when the printed circuit board suffers an impact, thereby affecting performance of chips on the motherboard.
When non-leaded tin balls are applied in the conventional motherboard, aforesaid things usually happen. Referring to FIG. 1, a conventional motherboard is shown, which includes a PCB 10′, a CPU chip 20′ and a north bridge chip 30′ arranged on the PCB 10′. Four securing holes 11′ are defined in the PCB 10′ around the CPU chip 20′. Four corners of the north bridge chip 30′ are designated with N1′, N2′, N3′, and N4′. A software LS-DYNA is used for simulating stress distribution on the tin balls at the corners of the north bridge chips in FIG. 1 when the PCB 10′ with heat dissipating modules mounted thereon suffer an impact. Simulation conditions are set as follows: the initial velocity of the PCB 10′ is 4.86 meters/second when the PCBs 10′ suffer an impact, and a maximal acceleration of four corners of the PCBs 10′ is determined to be 45 gravities. The stresses on the corners of the north bridge chip 30′ in the FIG. 1 during an impact are detailed in a table below:
CornerStress in megapascals (MPa)N1′205.3N2′99.27N3′94.3N4′149.7
As can be seen in the above table, the corner N1′ of the north bridge chip 30′ in the conventional motherboard nearest to the heat dissipating module of the CPU chip 20′ suffers a great deal more stress than others, and the lowest corner N4′ suffers the second most stress, which may exceed the maximum, stress value the tin balls can undergo. Therefore, the tin balls located at these corners are easily damaged by impact to the PCB 10′.
What is needed, therefore, is a new motherboard structure which provides good performance of a semiconductor chip in a circuit board even after the circuit board suffers an impact.